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39 results for “chromosomal speciation”
Speciation through chromosomal fusion and fission in Lepidoptera
<p>28 Mai 2020<br> Phylogenetic trees, the chromoSSE script and the input data for the chromoSSE models belonging to the publication "<strong>Speciation through chromosomal fusion and fission in <em>Lepidoptera" </em></strong>doi 10.1098/rstb.2019.0539. For more information, contact jurriaan.devos@unibas.ch or kay.lucek@unibas.ch.</p> <p>The zipped folder "trees" contains three posterior distributions of chronograms for each of 16 genera, based on a sample of 100 trees each.<br> Each tree includes the outgroup taxon, and the ingroup-outgroup split was dated based on one of three strategies:<br> - For the files named GENUS_tmax_pl.tre based on the reported maximum (oldest) age of the reported interval;<br> - For the files named GENUS_tmed_pl.tre based on the reported median age;<br> - For the files named GENUS_tmax_pl.tre based on the reported minimum (youngest) age of the reported interval.<br> Note that the outgroups were pruned prior to diversification rate analysis.<br> The median age files were used as input for the ChromoSSE analysis; all files were used an input for the analyses based on Brownian Motion.</p> <p>The file "chromoSSE.Rev" contains a script that runs the cromoSSE models.<br> Inorder to use this script RevBayes needs to be installed. This can be done by using the link: https://revbayes.github.io/download.<br> It can be run with the command line:<br> $> rb chromoSSE.Rev --args 1<br> As a argument every number between 1 and 16 can be used. And represent a genera:<br> 1 = Colias, 2 = Erebia, 3 = Eunica, 4 = Eurema, 5 = Heliconius, 6 = Ithomia, 7 = Lycaena,<br> 8 = Lysandra, 9 = Memphis, 10 = Morpho, 11 = Oleria, 12 = Papilio, 13 = Pieris,<br> 14 = Polyommatus, 15 = Pteronymia, 16 = Taygetis.<br> The process runs automatically and generates MCMC outputfiles and stores them in the directory "output".<br> Each tree that is analyzed returns three files:<br> -The files named "GENUS.ChromoSSE_anc_statesX.log" logfile of the states;<br> -The files named "GENUS.ChromoSSE_finalX.tree" tree output of the analysis;<br> -The files named "GENUS.ChromoSSE_modelX.log" logfile of the model.<br> The files can be easily accessed by using the software Tracer: https://beast.community/tracer</p> <p>The zipped folder "data" contains input files needed for the chromoSSE analysis.<br> To run each analysis a tree "GENUS.pruned.trees" and a tsv-file "GENUS.pruned.states.tsv" with the number of chromosomes per species is needed.<br> In the trees all species without a chromosom number were excluded.</p>
Pronounced differentiation on the Z chromosome and parts of the autosomes in crowned sparrows contrasts with mitochondrial paraphyly: implications for speciation
<p>When a single species evolves into multiple descendent species, some parts of the genome can play a key role in the evolution of reproductive isolation while other parts flow between the evolving species via interbreeding. Genomic evolution during the speciation process is particularly interesting when major components of the genome—for instance, sex chromosomes vs. autosomes vs. mitochondrial DNA—show widely differing patterns of relationships between three diverging populations. The golden-crowned sparrow (<em>Zonotrichia atricapilla</em>) and the white-crowned sparrow (<em>Zonotrichia leucophrys</em>) are phenotypically differentiated sister species that are largely reproductively isolated despite possessing similar mitochondrial genomes, likely due to recent introgression. We assessed variation in more than 45,000 single nucleotide polymorphisms (SNPs) to determine the structure of nuclear genomic differentiation between these species and between two hybridizing subspecies of <em>Z. leucophrys</em>. The two <em>Z. leucophrys</em> subspecies showed moderate levels of relative differentiation and patterns consistent with a history of recurrent selection in both ancestral and daughter populations, with much of the sex chromosome Z and a large region on the autosome 1A showing increased differentiation compared to the rest of the genome. The two species <em>Z. leucophrys</em> and <em>Z. atricapilla</em> show high relative differentiation and strong heterogeneity in the level of differentiation among various chromosomal regions, with a large portion of the sex chromosome (Z) showing highly divergent haplotypes between these species. Studies of speciation often emphasize mitochondrial DNA differentiation, but speciation between <em>Z. atricapilla</em> and <em>Z. leucophrys</em> appears primarily associated with Z chromosome divergence and more moderately associated with autosomal differentiation, whereas mitochondria appear highly similar due apparently to recent introgression. These results add to the growing body of evidence for highly heterogeneous patterns of genomic differentiation during speciation, with some genomic regions showing lack of gene flow between populations many hundreds of thousands of years before other genomic regions.</p>
Pronounced differentiation on the Z chromosome and parts of the autosomes in crowned sparrows contrasts with mitochondrial paraphyly: implications for speciation
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Data from: Dioecy and chromosomal sex determination are maintained through allopolyploid speciation in the plant genus Mercurialis
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Data: Chromosomal inversions and the demography of speciation in Drosophila montana and Drosophila flavomontana
<p>Chromosome-level genome assemblies of Drosophila montana and Drosophila flavomontana that are associated with the publication "Chromosomal inversions and the demography of speciation in Drosophila montana and Drosophila flavomontana" by Poikela et al. (2024).</p> <p>Dmontana_chromosomes = only D. montana scaffolds assigned to chromosomes</p> <p>Dmontana_all_regions = all genomic D. montana regions</p> <p>Dflavomontana_chromosomes = only D. flavomontana scaffolds assigned to chromosomes</p> <p>Dflavomontana_all_regions = all genomic D. flavomontana regions</p>
Lacustrine speciation associated with chromosomal inversion in a lineage of riverine fishes
<p>Geographic isolation is the primary driver of speciation in many vertebrate lineages. This trend is exemplified by North American darters, a clade of freshwater fishes where nearly all sister species pairs are allopatric and separated by millions of years of divergence. One of the only exceptions is the Lake Waccamaw endemic <em>Etheostoma perlongum</em> and its riverine sister species <em>E. maculaticeps</em>, which have no physical barriers to gene flow. Here we show that lacustrine speciation of <em>E. perlongum</em> is characterized by morphological and ecological divergence likely facilitated by a large chromosomal inversion. While <em>Etheostoma perlongum</em> is phylogenetically nested within the geographically widespread <em>E. maculaticeps</em>, there is a sharp genetic and morphological break coinciding with the lake-river boundary in the Waccamaw River system. Despite recent divergence, an active hybrid zone, and ongoing gene flow, analyses using a de novo reference genome reveal a 9 Mb chromosomal inversion with elevated divergence between <em>E. perlongum</em> and <em>E. maculaticeps</em>. This region exhibits striking synteny with known inversion supergenes in two distantly related fish lineages, suggesting deep evolutionary convergence of genomic architecture. Our results illustrate that rapid, ecological speciation with gene flow is possible even in lineages where geographic isolation is the dominant mechanism of speciation.</p>
Lacustrine speciation associated with chromosomal inversion in a lineage of riverine fishes
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Data from: Chromosome-scale inference of hybrid speciation and admixture with convolutional neural networks
<p>Inferring the frequency and mode of hybridization among closely related organisms is an important step for understanding the process of speciation and can help to uncover reticulated patterns of phylogeny more generally. Phylogenomic methods to test for the presence of hybridization come in many varieties and typically operate by leveraging expected patterns of genealogical discordance in the absence of hybridization. An important assumption made by these tests is that the data (genes or SNPs) are independent given the species tree. However, when the data are closely linked, it is especially important to consider their non-independence. Recently, deep learning techniques such as convolutional neural networks (CNNs) have been used to perform population genetic inferences with linked SNPs coded as binary images. Here we use CNNs for selecting among candidate hybridization scenarios using the tree topology (((P<sub>1</sub>,P<sub>2</sub>),P<sub>3</sub>),Out) and a matrix of pairwise nucleotide divergence (d<sub>XY</sub>) calculated in windows across the genome. Using coalescent simulations to train and independently test a neural network showed that our method, HyDe-CNN, was able to accurately perform model selection for hybridization scenarios across a wide-breath of parameter space. We then used HyDe-CNN to test models of admixture in <em>Heliconius</em> butterflies, as well as comparing it to a random forest classifier trained on introgression-based statistics. Given the flexibility of our approach, the dropping cost of long-read sequencing, and the continued improvement of CNN architectures, we anticipate that inferences of hybridization using deep learning methods like ours will help researchers to better understand patterns of admixture in their study organisms.</p>
Data from: Gene flow mediates the role of sex chromosome meiotic drive during complex speciation
During speciation, sex chromosomes often accumulate interspecific genetic incompatibilities faster than the rest of the genome. The drive theory posits that sex chromosomes are susceptible to recurrent bouts of meiotic drive and suppression, causing the evolutionary build-up of divergent cryptic sex-linked drive systems and, incidentally, genetic incompatibilities. To assess the role of drive during speciation, we combine high-resolution genetic mapping of X-linked hybrid male sterility with population genomics analyses of divergence and recent gene flow between the fruitfly species, <em>Drosophila mauritiana </em>and<em> D. simulans</em>. Our findings reveal a high density of genetic incompatibilities and a corresponding dearth of gene flow on the X chromosome. Surprisingly, we find that a known drive element recently migrated between species and, rather than contributing to interspecific divergence, caused a strong reduction in local sequence divergence, undermini ng the evolution of hybrid sterility. Gene flow can therefore mediate the effects of selfish genetic elements during speciation.
Data from: Recent speciation and elevated Z-chromosome differentiation between sexually monochromatic and dichromatic species of Australian teals
Sex chromosomes potentially have an important role in speciation and often have elevated differentiation between closely related species. In birds, traits associated with male plumage, female mate preference, and hybrid fitness have been linked to the Z-chromosome (females are heterogametic, ZW). We tested for elevated Z-differentiation between two recently diverged species of Australian ducks, the sexually monochromatic grey teal Anas gracilis and the dichromatic chestnut teal A. castanea. Despite prominent morphological differences, these two species are genetically indistinguishable at both mitochondrial DNA (mean ΦST < 0.0001) and 17 autosomal loci (mean ΦST = 0.0056). However, we detected elevated Z-differentiation (mean ΦST = 0.281) and tentative evidence of an island of differentiation on the Z-chromosome. This elevated differentiation was explained by a high frequency of derived alleles in chestnut teal that were absent in grey teal, which parallels independent evidence for a gain in dichromatism from a monochromatic ancestor. Coalescent estimates of demographic history and simulations indicated that the elevated Z-differentiation was unlikely to be explained by neutral processes, but instead supported a role of divergent selection. We discuss evidence for models of speciation with gene flow versus adaptive divergence in the absence of gene flow and find that both hypotheses are plausible explanations of the data. Overall, these teal have the weakest background differentiation documented to date for a species showing a large Z-effect, and they are an excellent model species for studying speciation genomics and the evolution of sexual dichromatism.
Data from: Chromosomal speciation in the genomics era: disentangling phylogenetic evolution of rock-wallabies
The association of chromosome rearrangements with speciation is well established, and there is a long history of theory and evidence relating to "chromosomal speciation". Genomic sequencing has the potential to provide new insights into how reorganization of genome structure promotes divergence, and in model systems has demonstrated reduced gene flow in rearranged segments. However, there are limits to what we can understand from a small number of model systems, which each only tell us about one episode of chromosomal speciation. Progressing from patterns of association between chromosome (and genic) change, to understanding processes of speciation requires both comparative studies across diverse systems and integration of genome-scale sequence comparisons with other lines of evidence. Here we showcase a promising example of chromosomal speciation in a non-model organism, the endemic Australian marsupial genus Petrogale. We present initial phylogenetic results from exon-capture that resolve a history of divergence associated with extensive and repeated chromosome rearrangements. Yet it remains challenging to disentangle gene tree heterogeneity caused by recent divergence and gene flow in this and other such recent radiations. We outline a way forward for better integration of comparative genomic sequence data with evidence from molecular cytogenetics, and analyses of shifts in the recombination landscape and potential disruption of meiotic segregation and epigenetic programming. In all likelihood, chromosome rearrangements impact multiple cellular processes and these effects need to be considered together, along with those of genic divergence. Understanding the effects of chromosome rearrangements together with genic divergence will require development of more integrative theory and inference methods. Together, new data and analysis tools will combine to shed light on long standing questions of how chromosome and genic divergence promote speciation.
Data from: The last bastion? X chromosome genotyping of Anopheles gambiae species pair males from a hybrid zone reveals complex recombination within the major candidate 'genomic island of speciation'
Speciation with gene flow may be aided by reduced recombination helping to build linkage between genes involved in the early stages of reproductive isolation. Reduced recombination on chromosome X has been implicated in speciation within the Anopheles gambiae complex, species of which represent the major Afrotropical malaria vectors. The most recently diverged, morphologically indistinguishable, species pair, A. gambiae and Anopheles coluzzii, ubiquitously displays a 'genomic island of divergence' spanning over 4 Mb from chromosome X centromere, which represents a particularly promising candidate region for reproductive isolation genes, in addition to containing the diagnostic markers used to distinguish the species. Very low recombination makes the island intractable for experimental recombination studies, but an extreme hybrid zone in Guinea Bissau offers the opportunity for natural investigation of X-island recombination. SNP analysis of chromosome X hemizygous males revealed: (i) strong divergence in the X-island despite a lack of autosomal divergence; (ii) individuals with multiple-recombinant genotypes, including likely double crossovers and localized gene conversion; (iii) recombination-driven discontinuity both within and between the molecular species markers, suggesting that the utility of the diagnostics is undermined under high hybridization. The largely, but incompletely protected nature of the X centromeric genomic island is consistent with a primary candidate area for accumulation of adaptive variants driving speciation with gene flow, while permitting some selective shuffling and removal of genetic variation.
Repeatome turnover meets stable chromosomes: repetitive DNA sequences mark speciation and gene pool boundaries in sugar beet and wild beets
<p>The present repository provides zipped archives containing the results of the RepeatExplorer2 runs of individual as well as comparative repeat analyses in beet genomes.</p> <p> </p> <p>Sugar beet (<em>Beta vulgaris</em> subsp. <em>vulgaris</em>) and its crop wild relatives share a base chromosome number of nine and similar chromosome morphologies. Yet, interspecific breeding is impeded by chromosome and sequence divergence that is still not fully understood. Since repetitive DNA sequences represent the fastest evolving parts of the genome, they likely impact genomic variability and contribute to the separation of beet gene pools. Hence, we investigated if innovations and losses in the repeatome can be linked to chromosomal differentiation and speciation.</p> <p>We traced genome- and chromosome-wide evolution across sugar beet and twelve wild beets comprising all sections of the beet genera <em>Beta </em>and <em>Patellifolia</em>. For this, we combined data from short and long read sequencing, flow cytometry, and cytogenetics to build a comprehensive data framework for our beet panel that spans the complete scale from DNA sequence to chromosome up to the genome. Genome sizes and repeat profiles reflect the separation of the beet species into three gene pools. These gene pools harbor repeats with contrasting evolutionary patterns: We identified section- and species-specific repeat emergences and losses, e.g. of the retrotransposons causal for genome expansions in the section <em>Corollinae</em>/<em>Nanae</em>. Since most genomic variability was found in the satellite DNAs, we focused on tracing the 19 beetSat families across the three beet sections/genera. These taxa harbor evidence for contrasting strategies in repeat evolution, leading to contrasting satellite DNA profiles and fundamentally different centromere architectures, ranging from chromosomal uniformity in <em>Beta</em> and <em>Patellifolia</em> species to the formation of patchwork chromosomes in <em>Corollinae/Nanae</em> species. </p> <p>We show that repetitive DNA sequences are causal for genome size expansion and contraction across the beet genera, providing insights into the genomic underpinnings of beet speciation. Satellite DNAs in particular vary considerably among beet taxa, leading to the evolution of distinct chromosomal setups. These differences likely contribute to the barriers in beet breeding between the three gene pools. Thus, with their isokaryotypic chromosome sets, beet genomes present an ideal system for studying the link between repeats, genome variability, and chromosomal differentiation/evolution and provide a theoretical basis for understanding barriers in crop breeding.</p>
Data from: Gene flow mediates the role of sex chromosome meiotic drive during complex speciation
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Data from: Chromosome-scale inference of hybrid speciation and admixture with convolutional neural networks
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Data from: The last bastion? X chromosome genotyping of Anopheles gambiae species pair males from a hybrid zone reveals complex recombination within the major candidate ‘genomic island of speciation’
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Data from: Chromosomal speciation in the genomics era: disentangling phylogenetic evolution of rock-wallabies
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Data from: Recent speciation and elevated Z-chromosome differentiation between sexually monochromatic and dichromatic species of Australian teals
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Data from: On the Coyne and Orr-igin of species: effects of intrinsic postzygotic isolation, ecological differentiation, X-chromosome size, and sympatry on Drosophila speciation
Coyne and Orr found that mating discrimination (premating isolation) evolves much faster between sympatric than allopatric Drosophila species pairs. Their meta-analyses established that this pattern, expected under reinforcement, is common and that Haldane's rule is ubiquitous in Drosophila species divergence. We examine three possible contributors to the reinforcement pattern: intrinsic postzygotic isolation, dichotomized as to whether hybrid males show complete inviability/sterility; host-plant divergence, as a surrogate for extrinsic postzygotic isolation; and X chromosome size, whether roughly 20% or 40% of the genome is X-linked. We focus on "young" species pairs with overlapping ranges, contrasted with allopatric pairs. Using alternative criteria for "sympatry" and tests that compare either level of prezygotic isolation in sympatry or frequency of sympatry, we find no statistically significant effects associated with X chromosome size or our coarse quantifications of intrinsic postzygotic isolation or ecological differentiation. Although sympatric speciation seems very rare in animals, the pervasiveness of the reinforcement pattern and the commonness of range overlap for close relatives indicate that speciation in Drosophila is often not purely allopatric. It remains to determine whether increased premating isolation with sympatry results from secondary contact versus parapatric speciation and what drives this pattern.
Data from: Experimental swap of Anopheles gambiae's assortative mating preferences demonstrates key role of X-chromosome divergence island in incipient sympatric speciation.
Although many theoretical models of sympatric speciation propose that genes responsible for assortative mating amongst incipient species should be associated with genomic regions protected from recombination, there are few data to support this theory. The malaria mosquito, Anopheles gambiae, is known for its sympatric cryptic species maintained by pre-mating reproductive isolation and its putative genomic islands of speciation, and is therefore an ideal model system for studying the genomic signature associated with incipient sympatric speciation. Here we selectively introgressed the island of divergence located in the pericentric region of the X chromosome of An. gambiae s.s. into its sister taxon An. coluzzii through 5 generations of backcrossing followed by two generations of crosses within the introgressed strains that resulted in An. coluzzii-like recombinant strains fixed for the M and S marker in the X chromosome island. The mating preference of recombinant strains was then tested by giving virgin recombinant individuals a choice of mates with X-islands matching and non-matching their own island type. We show through genetic analyses of transferred sperm that recombinant females consistently mated with matching island-type males thereby associating assortative mating genes with the X-island of divergence. Furthermore, full-genome sequencing confirmed that protein-coding differences between recombinant strains were limited to the experimentally swapped pericentromeric region. Finally, targeted-genome comparisons showed that a number of these unique differences were conserved in sympatric field populations, thereby revealing candidate speciation genes. The functional demonstration of a close association between speciation genes and the X-island of differentiation lends unprecedented support to island-of-speciation models of sympatric speciation facilitated by pericentric recombination suppression.
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International Brain Laboratory public data
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OpenNeuro
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